PROJECT SUMMARY/ABSTRACT Human immunodeficiency virus 1 (HIV-1) RNA genome is subject to covalent modifications through a variety of mechanisms. The roles of these modifications in HIV/AIDS and/or substance use disorders? prioritized by the NIH in this RFA?remain poorly defined. We have previously reported that an interferon (IFN) inducible gene, termed the Adenosine Deaminase Acting on RNA-1 (ADAR1), introduced A-to-I(G) mutations in HIV-1 rev RNA, particularly in the region of RNA encoding for Rev Response Element (RRE) binding domain, and in env RNA. These mutations inhibited the binding of Rev to RRE and the transport of primary transcripts like gag, pol and env from nucleus to cytoplasm. As a result, viral protein synthesis and virus production were impaired in both cell lines (293T, HeLa, Jurkat T) and primary CD4+ T cells. Furthermore, ADAR1 was active against a number of X4 and R5 HIV-1 of different clades; A-to-I(G) modifications of the env gene inhibited viral infectivity. Based on these findings, we hypothesize that ADAR- 1 mediated editing of HIV RNA attenuates the virus and hence impacts the ability of edited virus to enter latency. Interestingly, it has been reported that ADAR1 expression level and its editing activity is regulated by addictive substances. Hence, addictive substances may modulate HIV replication in reservoir cells of the central nervous system through regulating the ADAR1-mediated editing of HIV RNA. In this application, we plan to investigate whether ADAR1 induces A-to-I(G) mutations to HIV RNA genome, whether the edited virus alters in its ability in acquiring latency, and how exposure to addictive substances affects ADAR1- mediated HIV genomic RNA editing.